8331854: ubsan: copy.hpp:218:10: runtime error: addition of unsigned offset to 0x7fc2b4024518 overflowed to 0x7fc2b4024510

Reviewed-by: kvn, clanger

Author: MBaesken

src/hotspot/share/utilities/copy.hpp

@@ -211,6 +211,7 @@ class Copy : AllStatic {
     // byte_count is in bytes to check its alignment
     assert_params_ok(from, to, HeapWordSize);
     assert_byte_count_ok(byte_count, HeapWordSize);
+    if (byte_count == 0) return;
 
     size_t count = align_up(byte_count, HeapWordSize) >> LogHeapWordSize;
     assert(from <= to || to + count <= from, "do not overwrite source data");